30+ Online Electrical Machines Interview Questions

Electrical Machines Interview questions

Electrical Machines Interview questions

1. What is a single phase Autotransformer?

A Single-stage autotransformer is a solitary twisting transformer in which a piece of the winding is basic to both high-voltage and low-voltage sides.

2. What are the advantages of Autotransformer?

The benefits of autotransformer are as per the following: 
  • Less winding material is required if there should be an occurrence of the autotransformer. 
  • These transformers are not expensive. 
  • These transformers are littler in size. 
  • In Autotransformer ohmic misfortunes and center misfortunes are less. 
  • These transformers have high proficiency.

3. What are the disadvantages of Autotransformer?

The impediments of autotransformer are as per the following: 
  • If there should arise an occurrence of Autotransformer compelling impedance is littler. 
  • On account of open circuit twisting, full voltage is exchanged from the essential side to the auxiliary, and this can consume the hardware.

4. What are the applications of Autotransformers?

The applications of autotransformer are as follows:
  • These are used for the interconnection of the power system at different voltage levels like 132KV and 230KV.
  • In the distribution system, autotransformers are used to boost the supply voltage.
  • Autotransformers can be used for starting induction motors and synchronous motors if it has many tappings.
  • Autotransformers can be used as variac (variable a.c).

5. What is the general system requirement of Alternator?

There is a requirement of two types of system for the generation of e.m.f.
The Magnetic system is required for the production of the magnetic field.
Armature system is required for the houses of conductors on which the EMF is to be induced.

6. What are the advantages of Stationary Armature and Rotating Field System?

The upsides of the stationary armature and pivoting field framework are as per the following: 
  • The curls of the stationary armature can be protected effectively. 
  • The cooling of the winding is increasingly effective. 
  • In the engine high fringe speed can be accomplished. 
  • In this Slip rings and brushes are a bit much, and we can without much of a stretch supply the yield current to the heap circuit

What is meant by Stator? What is meant by Rotor?

  • In AC/DC motor or Generator, the stationary part of the system is called the Stator, and the rotating components of the system, i.e., either in generator or motor is called the Rotor.
  • What are the Advantages of the three-phase motor over Single phase motor?
  • The advantages of three Phase motor over single phase motor are as follows:
  • Starting Torques are higher.
  • Improved speed regulation is there.
  • Less vibration is there.
  • The operation is quite.

7. What is the basic principle of operation of Alternators/DC generators?

Alternators/DC generators chip away at the key guideline of Faraday?s law of Electromagnetic Induction. This law expresses that when we move any current conveying conductor in an attractive field, at that point an EMF is incited in it.

8. How to minimize the Eddy Current Losses?

Eddy current losses can be minimized by laminating the core and insulating the core from each other with paper or varnish.

9. What is meant by Turbo Alternators?

Fast alternators are called Turbo Alternators. In view of the rapid of revolution, the distance across of the rotor is diminished, and the hub length is expanded. In this two or four posts machine are utilized, and steam turbines are utilized as prime movers.

10. What are the various types of Rotor used in the Alternators?

The various types of a rotor are:
  • Salient pole Rotor.
  • Squirrel Cage Rotor.
  • Wound Rotor.
  • Cylindrical Rotor.

11. Define Pole Pitch?

Post pitch is characterized as the separation between the Centers of two adjoining shafts. In which one post pitch is equivalent to 180 electrical degrees. We can likewise depict it as the quantity of spaces per shaft.

12. Define Coil Span?

Coil Span is defined as the distance between the two coil sides of a coil. We can also express it in electrical degrees or many slots.

13. What is meant by full pitched winding?

Full pitched winding are those winding in which the coil span is equal to the pole pitch.

14. What is meant by short-pitched winding?

Short pitched winding are those in which the coil span is less than the pole pitch. These winding are also called as short-chorded winding.

15. Why the efficiency of a three-phase induction is the motor is less than that of a three-phase transformer?

The effectiveness of a three-stage acceptance engine is under three-stage transformer since three-stage enlistment engine resembles a turning transformer and as a result of the pivoting idea of enlistment engine there is contact and twisting misfortunes in it. Three stage transformer is a static gadget; in this way, there are no rotational misfortunes.

16. Why does curving the pole faces in a DC machine contributes to a smoother DC output voltage from it?

The recompense of the DC machine must be as perfect as workable for having smoother yield voltage. For good recompense, the transition thickness noticeable all around hole must diminish step by step from most extreme incentive under the focal point of the post to zero.

17. The series field winding has low resistance while the shunt field winding has high resistance. Why?

On account of the generator, the arrangement winding takes the full burden current along these lines, it requires not very many swings to create the vital attractive field, and in this manner the arrangement field winding has low obstruction. However, on account of shunt winding the shunt opposition has full burden voltage crosswise over it and requires countless to confine the current in it; subsequently, the shunt field windings has high obstruction.

18. What is a Commutator?

The gadget which changes over the substituting actuated emf of a generator to the DC emf is called Commutator. On account of the engine, it produces unidirectional torque.

19. What is meant by reactance voltage?

At the point when a curl experiences Commutation in a loop then an EMF is prompted, and this instigated EMF is called reactance voltage. 
An armature curl has certain self-inductance, and when the loop experiences replacement at that point there is an adjustment in current (di) in that curl, and the substitution takes certain time (dt) in this way the loop experiencing recompense has self-prompted EMF which is given by L(di/dt).

20. What is an AC motor?

Air conditioning engines are electric engines that are driven by a substituting flow. It comprises of two sections an outside stationary stator and inside the rotor. The external stators have curls that are provided by a substituting current to deliver a turning attractive field and inside rotor is connected by yield shaft, and the torque is given to it by the pivoting field.

21. What is a DC motor?

The machine that changes electrical vitality into mechanical vitality as turn is called DC engine. Its development is created by the physical conduct of the electromagnetism. The attractive field used to create development is delivered by the inductors inside them, or we can say that DC engines are precisely commutated electric engines that are driven by Direct Current (DC).

22. What is the Universal motor?

The engine which is intended to work on AC and DC control both is known as Universal engine or Series wound engine. It performs great on AC on the grounds that if there should arise an occurrence of AC the current in both the field and the armature substitutes in synchronism way and subsequently, the subsequent mechanical power happens the consistent way of turn.

23. Why do we perform an Open-circuit test and Short-circuit test on the transformer?

The Open-Circuit test and Short-Circuit test are performed to decide the circuit consistent, productivity and guideline of a transformer, without stacking the transformer. The power utilization of these heaps is less.